The present invention relates to a method and/or a measuring device for locating objects enclosed in a medium according to the preamble of Claim 1 and/or Claim 8.
A method of this nature, and/or a measuring device for carrying out this method utilizes a capacitive sensor device that generates a detection signal, e.g., in the form of an electromagnetic field, so that the detection signal passes through the medium to be analyzed, but, at the very least, penetrates the medium to a sufficient extent. An object enclosed in the medium influences the detection signal, so that an evaluation of the detection signal makes it possible to obtain information about an object that is enclosed in the medium.
A measuring device according to the general class, e.g., a stud sensor, detects an object that is enclosed in the medium by way of the change of the electrical capacitance of its capacitive sensor device, the change being generated by the enclosed object. An object that is enclosed in a medium changes the dielectric properties of the medium, so that a precision capacitor that is brought into the vicinity of the object senses a change in capacitance caused by the object and/or a change in its impedance. This capacitance change may be measured, for example, by the shift current of the precision capacitor of the capacitive sensor device.
A compact, hand-held stud sensor is made known in U.S. Pat. No. 6,249,113 B1. To locate objects behind a surface, the stud sensor measures the change in capacitance sensed by a sensor circuitry as the measuring device is moved across a wall. To display the exact location of an object enclosed in the medium, the measuring device according to U.S. Pat. No. 6,249,113 B1 comprises an LED array in an arrow-shaped format on the housing of the measuring device. When an object is detected by the measuring device, a pair of LEDs in the arrow-shaped LED array on the housing of the measuring device is activated as a function of the signal strength. As the sensor is scanned closer to the enclosed object, i.e., the stronger the detection signal that is generated by the object becomes, the further the activated LEDs travel toward the arrow tip in the LED array. When the measuring device is finally positioned directly over the enclosed object, the tip of the arrow in the LED array is illuminated. Basically, therefore, the measuring device according to U.S. Pat. No. 6,249,113 B1 makes it possible to locate objects enclosed in a medium, e.g., a wall. Neither the device disclosed in U.S. Pat. No. 6,249,113 B1 for locating objects enclosed in a medium, nor the very simple method on which it is based, are capable of measuring the depth at which the object is located.
Publication WO 94/04932 discloses a portable device for locating objects positioned behind a surface, comprising a sensor for sensing additional capacitive loading caused by the object, an evaluation unit for the detection signal, and a display for presenting the measured results. In addition, the measuring device according to WO 94/04932 comprises a device that allows the sensor device to be operated in a higher-sensitivity or lower-sensitivity mode.
Publication WO 94/04932 further discloses a method for determining the location of an object positioned behind a surface. To accomplish this, the corresponding measuring device is moved across the wall to be analyzed. The sensor according to WO 94/04932 is capable of sensing an increase or decrease in the thickness of the material. This permits the device to inform the operator, for example, that the sensor was calibrated incorrectly, e.g., directly over an enclosed object. The method on which this is based further makes it possible to inform the operator that the medium being analyzed is too thick or too thin for an enclosed object to be detected.
A digital register in the measuring device according to WO 94/04932 permits the calibration data to be stored indefinitely while the sensor is powered on.
A stud sensor is made known in U.S. Pat. No. 6,198,271 B1, which, in order to locate objects enclosed in a wall, detects the changes in capacitance of three capacitive sensors as the sensor is moved across the wall, the sensors being integrated in the measuring device. A comparison circuit monitors the relative charge time associated with each capacitive element, the charge times providing an indication of the relative capacitances of the three capacitive elements. Changes in the relative capacitances of the three elements as the device is moved along a wall are due to a change in the dielectric constant of the wall, which normally results from the presence of an object behind the surface over which the device is moved. The comparison circuit uses differences in the measured relative capacitances of the individual capacitive elements to locate the enclosed object.
The measuring device disclosed in U.S. Pat. No. 6,198,271 B1 includes a display that consists of a plurality of display elements that are connected with the evaluation unit of the measuring device in such a manner that only those elements that are located directly above the located object display a signal. In this manner, it is possible to center the measuring device over the located object and thereby indirectly determine the location of the object.